Error detecting code system



June 20, 1950 L. M. POTTS 2,512,038

ERROR DETECTING CODE SYSTEM Filed June 7, 1947 4 Sheets-Sheet l INVENTOR LOUIS M. POTTS, DECEASED MARTHA W. O. POTTS, EXECUTRIX BY 521 FM ATTORNEY June 20, 1950 L. M. POTTS ERROR DETECTING CODE SYSTEM 4 SheetsSheet 2 Filed June 7, 1947 oEcEAeo MARTHA W. C.-POTT$ i BYE? [P ATTORNEY INVENTOR LOUIS M. POTTS 8 EXECUTRI June 20, 1950 L. M. POTTS 2,512,038

ERROR DETECTING CODE SYSTEM Filed June 7, 1947 4 Sheets-Sheet 3 I iNVENTOR I LOUIS POTTS DECEASED L1 JMARTHA w. c. POTTS,EXEcuTR|x FIG. 3

I BY

ATTORNEY June 20, 1950 L. M. POTTS 2,512,038

ERROR DETECTING CODE SYSTEM Filed June 7, 1947 4 Sheets-Sheet 4 1 INVENTOR LOUIS M. POTTS.

DECEASED MARTHA W.O.POTTS cxacuTklx eff ATTORNEY Patented June 20, 1950 U NI TED STAT ES. I'QE 2,512,031; EBBQB nE'r crING com: sYs'rEM' Lquis M Potts, deceased, late of Evans'ton, 111., by Martha W. G. Potts, executrixl Evanstofi, Illl, assignor to. Teletype (Em gration, Chicago, 111;, a c rpo sti n o Dela 1'1 Glaims.

This invention relates to printing telegraph systems and apparatus, and particularly to an error detectingicode system which automatically detects errors in signal transmission.

in printing telegraph systems, especially where radio channels are 'used as a communicating medium, as distinguished from wire channels, atmospheric and other electrical disturbances may causeialse operations of printing telegraph ppara s Accordingly, an object of the present invention is to provide an error detecting code system wherein an error indication is recorded at a receiving station when message signals are not received as transmitted.

Another objec of the invention is to provide in a telegraph system means to transmit two groups of interleaved signals for each character, the individual signals or one group being opposite in nature to the corresponding individual signals of the other group and means to receive'said interleaved signalsand record normal characters when the individual signals of one group are 0pposite in nature to the corresponding individual signals of the other group. If the individual received signal elements of one group are not opposite in nature to the corresponding signal elements of the other group, an error indication will be recorded.

,A iurther object of the invention is to provide a single channel error detecting code system which may be readily converted into a two channel multiplex system having no error indicating feature.

Stillanother object of the invention is to provide a single channel error detecting code system which may be readily converted into a system wherein a single transmitter may transmit identical signals to a plurality of distant recorders.

Other objects, features, and advantages of the invention although not specifically recited above will become apparent as the invention is described in more detail.

In the proposed error detecting .code system,

each element of a live unit signal code combination is transmitted twice, once in a normal manner and immediately thereafter in an inverted manner. Two groups of interleaved signals are, therefore, transmitted for each character with the individual signals of one groupbeing opposite in natur o c r ondin n i idu l i nals o the other group, Since it is unlikely that static .or other i r erence ro uce wounq s i r i b e tin a d dt 'ng si n im s aiel h- .staciial v th same tim stone s sismssisa a very reliable error indicator. In such a system, it is almost certain that eitherthe normal or the inverted signal will come through to the receiver and act as an error indicating control medium as will hereinafter appear.

In one embodiment of the invention, signals to be transmitted are acquired irom a tape transmitter and stored in aset of five storage relays. The storage relays, in addition to having the usual lockingcontact tongues, are each provided with an operating contact tongue which is connected tobattery and moves between a front and back contact. The front contacts are individ ually connected with the normal segments of a distributor, while thebackcontacts are connected to the segments which 'control the transmission of inverted signals. The normal and inverted transmitting segments of the distributor are interleaved or alternated with respect to each other, so that :an inverted signal invariably follows the normal signal to which it is related. It is thus evident that when transmission is taking place, each operating contact tongue of a particular storage relay will either be resting on the normal frontcontact orthe inverted back contact. If a particular operating contact tongue is resting on its front contact, the normal transmitting 'seg ment connected therewith causes the transmissionof a current impulse when it is traversedby therilaistributor brush and the immediately following inverted segment will transmit a no current impulse. On the other hand, when a particular contact tongue is resting on .its backcontact, the normal transmitting segment connected there'- with, when traversed by the distributor brush, causes the transmission of .a no current impulse and the immediately following inverted segment rliil transmit acurrentimpuls .A radio system of communication discloSQd in the present in: vontionhutit will he understood that the invens not onfin d to u e and mayfind applicati n inwi eci systems or o he m ans. 9; communication. 1

'lhe inc mi g in e leaved s nals are sto ed y f a r ceiv n distr bu o o said relays rea s.-

signals and one which receives inverted signals do not respond in an opposite manner, a chain circuit will be broken causing the de-energization of an error indicating relay and the printing of an error indicating character. The printer employed in the present invention is of the type shown in the patent of Kleinschmidt, No. 1,567,599. When undistorted signals are received, a set of five printer code magnets are selectively operated to print normal characters, by means of a selector such as is shown in the afore-mentioned patent.

A modification of the proposed error detecting code system has for its main feature the provision of switching means at the transmitting and receiving ends of a line which may convert a. single channel error detecting system into a two channel multiplex system having no error detecting feature. In the two channel system, the signal code combinations of the individual transmitting stations are interleaved with respect to each other, element by element. This modification might be useful when reception is good and interference is at a minimum. Under these operating conditions, the error detecting feature would not be necessary and the manual switch could be moved to its two channel multiplex position to handle extra traffic.

By operating only the switching means at the receiving end of the line, a single transmitter may transmit identical messages to a pair of recorders and thus further flexibility is added to the invention.

Figs. 1 and 2 are schematic circuit illustrations which illustrate respectively the transmitting and receiving ends of a communication channel involved in the main embodiment of the invention; and

Figs. 3 and 4 are schematic circuit illustrations which illustrate respectively the transmitting and receiving ends of a communication channel involved in another embodiment of the invention. 2 With reference to Figs. 1 and 2, the first embodiment of the invention will now be described. Numeral l6 represents a, five unit code tape transmitter which may be of any conventional type with modifications in accordance with the present invention. A continuously rotating distributor is shown at H which is associated with a radio transmitter l2 by means of which outgoing signals are modulated.

Transmitter includes the usual transmitting cam sleeve l3 whose rotation is controlled by a clutch start magnet l4. When it is desired .to start the transmitter: Ill, switch It is closed and as brush arm H of distributor sweeps over segment l8, an obvious circuit is made for relay |9 which looks up through its contact tongue 2|. An obvious circuit is also established through contact tongue 22 of relay IQ for energizing clutch start magnet I4 thereby releasing cam sleeve i3 for rotation.

' According to the operation of a series of tape sensing levers 23 gooseneck transmitting levers 24-! to 24-5 are allowed to operate to provide a selection on the transmitting contacts 26-| to 26-5. At the same time that brush arm I! is "traversing the segment 18, a bail (not shown) :is then fed forward to a new position by means not shown and the bail allows the sensing levers to thereafter feel for a new code combination in "the tape. At the time the sensing levers 23 are 4 withdrawn, the tape is stepped and the sensing levers 23 are again allowed to feel for a new combination, gooseneck transmitting levers 24-| to 24-5 ride on the high part of associated transmitting cams 27, maintaining an open condition of all transmitting contacts 26-| to 26-5. However, by the time brush arm I! moves past segment I8, transmitting levers 24-| to 24-5 are free to operate in accordance with the new selection provided by the tape. It is thus seen that the transmitting levers 24-| to 24-5 maintain their operated positions for the greater portion of a revolution of cam sleeve 3.

When distributor brush arm I! traverses segment 28 a circuit is established over lead 29 for control relay 3|. As control relay 3| attracts its contact tongue 32, a locking circuit is broken for the upper three storage relays 33-|, 33-2 and 33-3 which extended over lead 34. As contact tongue 32 moves to its front contact it causesthe energization of a slow-to-operate relay 36, which now attracts its contact tongue 37 and. provides a ground circuit extending over lead 38 for transmitting contacts 2B-|, 26-2, and 26-3, which just previously have been set according to the new code combination in the tape. If any of the just mentioned transmitting contacts are operated, a circuit will be completed to the associated storage relays 33-|, 33-2, and 33-3 which are now set in accordance with the new code combination provided by the tape. Since relay 35 is slow-to-operate, ground will be extended through contact tongue 3! for a suihcient interval of time to allow contact tongue 32 to fall against its back contact without breaking the circuit to any of the storage relays 33-|, 33-2, and 33-3 which may be energized. It should be noted that when the contact tongue 32 moves away from its back contact as was explained above, the locking circuit for storage relays 33-|, 33-2, and 33-3 is broken and the previous selection stored in these relays is erased.

. When distributor brush arm I! traverses segment 40 a circuit is established over lead 39 for the control relay 4|. When control relay 4| is energized its contact tongue 42 moves from its back contact breaking the locking circuit extending over lead 44 for storage relays 33-4, 33-5, erasing the selection previously stored in these particular storage relays. As contact tongue 42 moves to its front contact, it closes a circuit for a, slow-to-operate relay 46 which, through the operation of its contact tongue 47, now provides a ground circuit extending over lead 48 for transmitting contacts 26-4 and 26-5 if they are op- ,erated at this time. In this manner a new selection will now be established for the storage relays 33-4 and 33-5. It is apparent that relays 4|, 46, function exactly like relays 3|, 36 to erase the previous selection stored thereby and establish a new selection therein.

In addition to the locking contact tongues 5|-| to 5|-5, stor ge relays 33-| to 33-5 are provided with operating contact tongues 3il-l to 30-5 which move between front and back contacts. The front contacts are connected to the normal transmitting segments 52-| to 52-5 of distributor while the back contacts are -a. front contact or a back contact to the radio transmitter |2 as the distributor brush arm traverses the individual transmitting segments.

"hy ineansof receivi I B l-FA to 6l-5A'of the-rec'ewm' distributor s further when that "ii/current through tr nsnnmngsegm nttzno urifnt passjthrough its companion transn'iitting "segment '52-lA, "and in a like manner the remaining fo'tir'pair's of transmittingsegxnents 'will nefdperatee. Conversely, ifn'o currentds passed ftniodgn'thetransmlmng segment 52- 1 cu'rrem em new through "the transmittin segment "51- I A and in a like manner tl'ie rernaining four "er transmitting segments will be *ope'i'af'tefd.

dd that "ft lie i'traiismitting distributor at the "transmittin ta'tibn and the receiving distributor at the Te- "station may be synchronized in any :6iiventior1"al *manner. At "the "receiving station therefis located a'radio receiver 60' which de- "ffiodulates incoming signals "and I accordingly opin-ates "a receiving relay 62 causing its contact 63 to move back and forth'in accordance fwithincomin'g signals. Such incomingsignals ng segments 't'l-l "to "61-5 ,66 "are transferred to a set of; five'pairs of "pri- 'rstora e relays 's1--| to 1 61-5 and "Bl-IA 1 .71 4 .i i N Whehhistributor brush arm-cs1 reaches "s'e'gnient ss, a circuitls completed lover le'a'd 69 for control relay H which now operates and b reaiks "ajmering circuit by 'at'tractingfit's tongue 12, ieiit difig 'Over lead '13, through the locking tongues 14-I'to14-3 and IE-IA to l4-3'Afor ias s'o'ciate'd secondary storage relays "It-l to "16-3 and IS-IA to '15-3'A, ei"asingthe pre- 'fvious"selection existing in these relays. When contact tongue 12 of'ico'ntrol "relay 'H moves "against its front contact a circuit "is established "fi'drtheslow-to-operate relay' 11 which noiw'at- "itra'c'ts its contact tongue 18 and provides a lig'round' circuit for contactton'gues" 19-! to 1-9-3 and IS-1A to IS-3A of associated 'prirna'ry storage r'eays'B'I-I to ""61-3 and "GT-FA to fry-3A. Contact tongues 1-9-1 to 19-3 and W-IA'to 19-3A'willhave been setaccording to "the previous code "combinati 'rceived the "primary storage "relays and --"wu1, accordingly transfer their selection over associated leads "TB-3A. "Itis'"'apparentffthat[relays "'1 l "and "1 T op- "fefrate in'a manner snnnarte'remys 3'1 36, "and "41, l'li describedin Fi'gfl When"Seg'n'ient 82 is "reached" by distributonbrush arm es-1' an obvious jc ircuit' is established for relayia which now at- "ltralcts its contact tongue 81 tobfak "a 1 locking circuit which was established "over "lead '90 jithrougn contact tongues "St-l to*8B-3 "and fS-FA to tit-s Ador theupper"three"pair of "primary storage relays *61-1 to fist-3 and "fil -lA to B'I- 3A,"readyin'g theserelays tore- 'cei've the -next incoming signal "code combina- "tion. It isthus observalilefthere fore, that durthe traversal ofsegment B'T'bybruSh "arm 461,3"iitinia1y "storage relays 61-! to til-3 and 'Gl-IA to Bl-3A are released 'inf'prdp'arajtion-for '81 a readily traceable circuit :is made "for *relay 88 which new energizes to "move its contact tong-ue tiirom its back contact :to its Ltront contact. this "breaks a. locking circuit extending over lead 9|, through contactt'ongues 14-4, 14- 5, and 'll-5A I for secondary storage frl'ai s "TS-'4, HS-5, 16-4Agand 5| G-ASA, aerasing "theprevious selectio existin in these storage "relays. when contact tongue 89 of control we- "la'y -88 moves against its front contact, it ces- 'tabIisHes-a'circuit for a slow-to-opera'teirelay 92 which by attracting its contact tongue $i3now provides a ground circuit extendin lover r94 'ifor *contact -tongues 19-4, 19-5, '19-"4'A, and "l b-5A of primary "storage relays ot- 4, 981-5, d G'I-UA =-'6'I-'-5A which have previously n freezes "up in accordance with the last i sign'al 'r'eceived thereby. 'A setting is now transferr'e' d ever leads 8l-4, 81-5, B-l-IA 8 *''5A to associated secondary storage relays 16 4, Hi- =5, "Hi-4A -and TS-5A which again lock up through their locking contact itongues as was described in "conne'ction'lwith relay "H When distributor brush: arm-"461 traverses seg- 5 ment 65 a "circuit is completed. for relay '10 which now attracts its "contact "tongue '15, fthereby breakinlg'a locking circuit existing-over lead 80 and through contact tongues 83-4, *8'6-5 and 86-41; and BB-BA-"of primary storage ao rlays fill, G'I-Ej 'Ei'I-Q'A and S'I-EA, thereby erasing a previous selection existing in these 'relays and preparing them for the reception :of "the next incoming signal.

'Thefsecondary "storage relays are also pro- "videdvvith "a 'seri'es of contact operating tongues "95- 1 GO QS-SQQ'G-IA'tO 9B-5 A and"9"l-l to 91-5 and "S'I-IA to 'QT-EA. Each pair of contaottongues, 96-1, "SJ'B-IA for 'examplefw'hen oppo'sitely operated as'the signals are-receivedas transmitted, *c'auses a *completionfof "the cir'onit *toanassociated code magnet 98-1. 'The :re- "rnaining'printer code magnets 98-? to 98-5 are "operated in a similar manner. The code magnets 98-! to '98-5 are usd'in 'a receiver "s'uch as "isdisc'losed in the patent of Klein- -'-schmidt, No. 1,567,599jissued December 29;1925. when the's'ignals are bein'g received without errors,"'contact tongues "QT-l and Bl-YA are' al- "ways oppositely operated and since the remainin'gcQntact'tOnguesQ'I-Z to 91-5 "and Ell- 2A "'tO'H'I-SA operate in a similar mannenachain "circuit istraceable to an error controlling relay 99." Holwever, if interference or other conditions "cause a pair'oi contacttongu'esto operate to like positions, the chain circuit will be bro-kenyand rlay 99 will release its tongue [N ta-complete a "circuit ror'anerror indicating magnet I0 I.

"The code magnets 98-I to 98-5 and error indicating magnet "I I! l are 'part of i aselector indi- 5 'cate'd generally as numeral I 02 Which is similar to a'slector shown in the previously mentioned 'Kleinschmidtpatent. The code magnetsSS-I to 98-5 selectively control the setting of individ. nally associated code bars Hi3 while'an added 'sixth'error indicating code'bar I04 is operable under the control of error indicating magnet IDI. "Whenc'ode bar i 04 is operated, it causes the printing of an error indication and blocks printing of allthenOrmaIcharacters. A' printermagnet I06 7ois'a1soprovided which is similarto'the printer 'magne't' t53 shown in theKleinsc'hmidt patent. According to the operation of code magnetsB'8-l "to"98"5 and error magnet [6 I, code bars'IO'3 and H14 are per'miss'ibly' allowed to "moveto the right 16 and close thecontact F01 to 'therebyenergize the printer magnet 106 over lead 108 when" segment 109 is traversed by the distributor brush arm 461. It is to be understood, however, that code bar '104 moves to the right only upon the reception channelexactly as was described in the first embodiment of the invention; that is, each signalv element is transmitted twice, once in a normal manner and immediately thereafter in an of n improper i nal, 5 inverted manner for error detection purposes.

In order to make clear the operation at a receiv- However, it will be noted that now the back coning station, a summarized description will now be tacts associated with contact tongues 30-1 to given, it being assumed that the receiving dis- 30-5 of storage relays 33-1 to 33-5 instead of tributor 66 is rotating in synchronism with the being connected directly to segments 52-1A to distributor 11 at a transmitting station. As dis- -1 52-5A are now connected through swinger contributor brush arm 46'! traverses segment 68, a tacts 211-1 to 211-5, when control relay 210 is rselection stored on contact tongues 19-1 to 19-3 de-energized, by the connection of leads 214-1 to :and IS-1A to IS-3A of primary storage relays 214-5 with individually associated leads 216-1 :61-1 to 61-3 and 6'1-1A to 61-3A is transto 216-5. When the A channel is transmitting ferred to second storage relays 16-1 to '16-3and under these conditions, the B channel transmitflB-IA to IS-3A after the selection previously I ter remains idle. 1 existing in these last-mentioned relays has been When it is desired to convert to a two channel erased as described in detail above. When segmultiplex system without error detecting, switch ilcnenti82 istraversed by distributor brush arm 61 211 is moved to its lower position and upon the the selection existing in primary storage relays 0 next rotation of brus a m 1 W S ent 1 61-1 to 61-3 and 6'1-1A to 6'l-3A is erased is reached, a circuit extends over lead 219 through and these relays are now ready to receive the switch 211 and through the winding of relay 221. next signal code combination. Relay 221 pulls up its locking contact tongue 222 When segment 81 is traversed by brush arm 461 which is now in series with contact tongue 223 the signals stored on contact tongue 19-4, 19-5, of relay 224. Closure of contact tongue 226 pro- 13-4A and IQ-5A of primary storage relays vides an obvious circuit for start magnet 14-3 51-4 51 5, s1 4 nd 51. 5 e transferred assuming that switch IB-B has been previously to secondary storage relays 16-4, 16-5, IS- 1A closed. Now when the distributor brush arm I! and l6-5A after the previous signal existing in traversed segme as just explained, relays 19 these last-mentioned relays has been erased as 0 and 221 are simultaneously pulsed so that start previously described. When segment 65 is crossed magnets 14 and 14-3 are energized at the'same by distributor brush arm 45! the selection existtime, thus providing synchronism betweentransing in primary storage relays 61-4, 61-5, 61-4A mitters A and B. and 61-5A is erased, preparing these relays for At this time contact tongue 231 has also been the reception of the next signal code combination. 5 drawn up by el y 1 so at W brush, arm 1 Failure of the secondary storage relays 16-1 reaches se e t an pulse is provided over to 16-5 and It-1A to It-5A to respond oppolead 232 through contact tongue 231, and through sitely with respect to any individual pair thereof e i di of Control ay 2H3. Cont/1'01 relay will break the chain circuit existing to error 210 n w l k p through s Contact e iifl control relay 99 and cause the printing of an error which is in series with contact tongue 233 of indication character. On the other hand, when relay 234. As a result, the circuit pat previousreception is normal, as segment M39 is traversed y extending from the back contacts of tongues by brush arm 461, a circuit will be completed to 5 0f relays 33-1 to 33-5 to segthrough contact H11, over lead 108, and the ments 52-IA to 52-5A of distributor 11 are now printer magnet 136 will operate to print a norbroken w Circuit paths are now made which mal character. It is to be noted that ifan all .1spacing or idle signal is received without distortion, none of the code magnets 98-1 to 98-5 or error magnet 161 will operate. Therefore, contact 101 will not close and no printing operation will take place. No special. idle signals are re- I iquired as in the seven unit radio code system 1 since the present system always insures that signal reversals will be provided forv synchronism extend from the back contacts of tongues 30-1B 31 as follows: from lead 29 over the conductor purposes, v 55 231, through swinger tongue 213 (now closed), The second embodiment of the invention, and over the lead 238 to the winding of relay (shown in Figs. 3 and 4:, will now be described with 3 In a Similar manner relay y the understanding that like parts appearing in now receive p s from e d b or Simulboth embodiments of the invention will be simitaoeously w t relay 41 v the l ng cirlarly numbered and that the description will not to f o d 39, over conductor ou ,be repeated except where necessary to give a full S ng tOngue 2 (HOW closed) OVEI Conductor understanding of the second embodiment of the 1and rou the winding of relay ..,;invention. It will be recalled that the feature of N m l r i n w proceeds over the A and the embodiment of the invention now being con- 3 Ch s With e signals of e two Chansidered is that it enables a single channel error 33 1161s interleaved- It Should b o ed that the i di ti system t b converted t tw signals transmitted on channel B are inverted channel multiplex system without error indica- Since n Contact tongues 3 t0 305B fall 1, away in response to the receipt of spacing im- "I'here is shown in Fig. 3, two transmitters, an P 5 by their aSSO d lays 33-1Bto 33-58,

A channel transmitter and a B channel transbatter is supplied to segments 52-1A to 52-5A mitter. When a control relay 216 is in its de-energized condition its contact swingers211-1 to 211-5 are resting on their backjcontacts and contact tongues 212 and 213' are'u nattracted so ,that transmission may take place over the A of, distributor 11. This inversion helps to maintain synchronism between transmitting and receiving stations when idle signals are transmitted. The details of this method of phasing are not described herein but are well known in the art.

The inverted'signals are, returned to normal by the, B. channel receiver. as, will appear later in the. description.

When it is desired to return to a single channel system with inverted signals for error detecting purposes, switch. 2H is moved to its upward position and on the next rotation of brush arm I! a circuit is established-extending from; segmentv l8'over lead 2 I 9 and through switch, 21.! tov relay 224. This causes contact tongu 22.3 of. relay 224 to be drawn. up and thus breaks the. locking circuit for relay 2.2l causing the contact tongues of the latter relay to fall away. When segment 40 is reached by brush arm l! the circuit. extends over lead 232, through contact 23! (now against its back contact), and through the winding of relay 234 which now energizes and pulls up the contact tongue 233. This breaks the locking circuit previously extending through con.- tact tongues 233 and 230 for relay 2 In which now becomes de-energized and its swingers 2| ll to 2|5 and H2, 213, move back to their error detecting position. It will, be noted that the circuit for start magnet l4-B isbroken as contact tongue 22,6. falls away upon de-energization of relay HI and. therefore transmitter B comes to rest while transmitter A may now sense signals with the error detecting feature.

At the receiving terminal shown in. Fig. 4, there is. provided in. addition to an A- channel printer, which operates exactly like the printer shown in 2. when the single channel error detecting code is. used, a B channel printer which is used when the system is converted to a two channel multiplex. The 3 channel printer is provided with code magnets 98-!B, to 98.5B and a print-- ing magnet lll6B. When the error indicating system. is used the B channel printer is idle and only the A channel printer is operated. With control relay 350 de-energized, contact tongues 351-4 to 35l5, and tongues 352 and 353 are in theirv unattracted positions and the circuit opcrates exactly like the circuit shown in Fig. 2. However, it will be noted that contact tongues 96l to Mir-5 of relays 16-4 to 'i65. are now associated with their companion contact tongues 9 6.|A. to 86-5A of relays FE-4 to, -5 as fol-. lows: from leads 3.54-.l to 354..5, through swinger contacts l.- l to- 35!-5 of relay 350 to leads. 356-| to 35'65.

When it is desired to place the receiving end, of the line in conditionfor two channel multiplex reception. without error detection, switch 35.3 is moved to its leftward position. When segu nt 358, of distributor 6,6 is traversed by brush. 4.6.! a, circuit is madefor relay 35.0..which. extends. over lead 359 andthrough switch. 351. Relay 35 therefore, operates and pulls up its locking tongue 3.6.1, which is'in series with tongue 352. of relay. 363. All swingers 35l-l to 35|5 and 352.. will now be. pulled, against their back contacts. Swinger 353 moves 011 its contact to open the cir-. quit. for error code magnet llll which extends over lead. 3.6.4 since error detection is not used in the two channel multiplex system. With. swinger tongues 35l-l to 35l5 of relay 35.9 against their front contacts the previously described circuits extending therethrough. are broken and leads 355-4 to 3565 associated with contact tongues 5B--|A to 965A of relays Ht-1A. to 1.6,5A are now connected through swinger tongues 35l| to 35.|l-5 to leads 356! to 366-5.. which individually extend to related. code mag-. nets 98-43 to 9 8-5B. Since relays 1E IA to l6.-5A perate in an. inverted manner to re.-

ceive. incoming signals, that is, their contact tongues. fall away in response to. spacing conditions. the signals for code magnets 98--IB are now returned to normal. This is due to the fact thatwhen tongues 96.--|A to 9'B5A move away from relays l6-|A to IE-5A in response to spacing or no current conditions, circuits indicative of marking conditions are completed to individually selected code magnets 98-13 to 98-53. Ground for contact tongues 96-.-I to 96-5 of relays 16.l. to, HF-5, is now provided over leads 3.54-4- to 354:5 to contacts 31l.l to 3'! l-5,since swinger tongues. 351:4 to. 35-l--5, when moved oil their back contacts, allow these just described circuits to be established.

When swinger 3.52 of relay 3,50 closes its con. tact, printer magnet. HIS-B will operate in a man.- ner similar to. printer magnet L36 due to the cir-. cuit provided over lead 312 and through-tongue 352 to lead 3'i3. Thus with the. control relay 35B. energized, signalsv received bydistributor 6.5 are alternately allocated to the A channel and B channel printers, which function in a manner disclosed in the previously mentioned patent to Kleinschmidt. 1

When the receiving station, is to. be returned to a single channel error indicating system, manual switch 315! ismoved to-the-rig-ht and upon the next rotationofbrush arm 4.6.1 of. distributor 66 an impulseisprovided from segment 358which extends over. lead. 35.9; andv throughswitch 35% to, relay 36.3. Relay. 3.63. is, therefore... energized-at tracting. its contact tongue 362 and breaking the locking circuit, previouslyexisting for relay 350-.

; When this. occurs, contact swingers 35l -l. to

35.l.5,, and 35,2, 353, areallowedto move tothein leftward Positions re-establishing the single channel circuit for error detection purposesv and again placing the B. channel printer in anidle condition. 1

It should be observed that in connection with- Figs. and. 4, ii. switch- 351 (Fig. 4) is operated to its rightward position and switch 2H, (Fig. 3 isallowed to. remain. in its: upward position... both recorders. A andBmay, print identical messages. provided, by the A, transmitter without the error indication feature. Thus, by such an. arrangement. the flexibility of the system is increased.

Various, changes. and. modifications may be made in. theinvention without. departing from thespirit and scope, thereof except. as definedin the appended claims.

Whatisclaimed is: 1. In an error indicating telegraph systemhaving. transmitting. and receiving stations, means at. said. transmitting, station for sending, each element of, a, signal code combination once in. a. normal manner and once in an, inverted manner, receiving means. at. said receiving station, for receiving. said, normal and. inverted signals, a, seriesof pairs of storage devices oper-.

able by said. receiying. means, one of the individual storage devices of. each of. said. pairs oil storage devicesbeing. responsive to normalsignals a d he, other to. inverted, signals, recording means at. said receiving. station. responsive to the opposite operation of the individual. storage. devices of each pair of said. Storage devicesfor recording normal. characters, and. an error indicating means. forming. a. part of said recording. means. o. record. an error. indicating character. upon the failure, oithe individual storage. devices. of any pair to be oppositely Operated with respect. to each other.

2. In an error indicating telegraph system hav-v ing transmitting and receiving stations, means at said transmitting station including a signal transmitter distributor for sending each element of a signal code combination once in a normal manner and once in an inverted manner, receiving means at said receiving station including a signa1 receiver distributor for receiving said normal and inverted signals, a series of pairs of storage devices operable by said receiving means, one of the individual storage devices of each of said pairs of storage devices being responsive to normal signals and the other to inverted signals, recording means at said receiving station responsive to the opposite operation of the individual storage devices of each pair for recording normal characters, and an error indicating means forming a, part of said recording means to record an error indicating character upon the failure of the individual storage devices of any pair to be oppositely operated with respect to each other.

3. In an error indicating telegraph system having transmitting and receiving stations, means at said transmitting station for transmitting each element of a signal code combination once in a normal manner and once in an inverted manner, receiving means at said receiving station for receiving said normal and invertedsignals, a first series of pairs of storage devices operable by said receiving means, a second series of pairs of storage devices, means for transferring signal code combinations from said first series of pairs of storage devices to said second series of pairs of storage devices, recording means at said receiving station responsive to the opposite operation 01' the individual storage devices of each pair of said second series of storage devices for recording normal characters, and an error indicating means forming a part of said recording means for recording an error indicating character upon the failure of the individual storage devices of any pair of said second series of storage devices to be oppositely operated with respect to each other.

4. In an error indicating telegraph system, means for transmitting each element of a signal code combination once in a normal manner and once in an inverted manner, receiving means for receiving said normal and inverted signals, and means controlled by said receiving means for recording normal characters in response to said normal and inverted signals being received by said receiving means as transmitted by said transmitting means and including means for recording an error indicating character in response to for any given element of a signal code combination a normal and an inverted signal not being received by said receiving means.

5. In an error indicating telegraph system having transmitting and receiving stations, a transmitter distributor at said transmitting station, signal generating means, a series of storage devices for storing signals provided by said generating means, means oppositely operated in respon e to the operation of the individual storage devices of said series of storage devices and associated with said transmitter distributor to enable said transmitter distributor to transmit each element of a signal code combination once in a normal manner and once in an inverted manner, receiving means at said receiving stations for receiving said normal and inverted signals, recording means at said receiving station for recording normal characters in response to each signal being received at said receiving station as transmitted by said transmitting station. and means forming a part of said recording means for recording an error indication in response to in a given element of a signal code combination a normal and an inverted signal not being received by said receiving means.

6. In a telegraph system, a transmitting distributor for sending first and second groups of interleaved signals, a first transmitter connectible to said distributor for providing two groups of interleaved signals for transmission by said distributor, each group being of an opposite nature than the other, a receiver distributor for receiving said first and second groups of interleaved signals, a first recorder connectible with said receiver distributor for recording normal characters in response to signals being received as transmitted, an error indicating means forming a part of said recorder operable in response to for any given element of a signal code combination opposite signals not being received, a

second transmitter connectible to said transmitter distributor, a second recorder connectible to said receiver distributor, switching means for connecting said second transmitter to said transmitter distributor and for thereby enabling said first and second transmitter to each transmit only a single group of interleaved signals, and switching means for connecting said second recorder to said receiver distributor to enable each of said recorders to receive a single group of the interleaved signals.

'7. In a telegraph system, a transmitting distributor for sending first and second groups of interleaved signals, a first transmitter connectible to said distributor for providing two groups of interleaved signals for transmission by said distributor, each group being of an opposite nature than the other, a receiver distributor for receiving said first and second groups of interleaved signals, a first recorder connectible with said receiver distributor for recording normal characters in response to signals being received as transmitted, an error indicating means forming a part of said recorder operable in response to for any given element of a signal code combination opposite signals not being received, a second transmitter connectible to said transmitter distributor, a second recorder connectible to said receiver distributor, switching means for connect-' a single group of interleaved signals, and switching means for connecting said second recorder to said receiver distributor to enable each of said recorders to receive a group of the interleaved signals, said error indicating means being disabled when both of said recorders are connected to said receiver distributor by said last-mentioned switching means.

8. In a telegraph system, a transmitter distributor for transmitting a first and second group of interleaved signals, a transmitter connected to said distributor for providing two groups of interleaved signals for transmission by said distributor, each groupbeing of an opposite nature than the other group, a receiver distributor for receiving said first and second groups of interleaved signals, a recorder controlled by said receiver distributor for recording normal characters in response to signals being received as transmitted, and an error indicating means forming a part of said recorder for recording an error indication in response to for any given element of a signal code combination signals of opposite seismnature not being received by said receiver dis tributor.

' 9. In a telegraph system, a transmitter distributor including alternately arranged, segments for'transmitting a first and second group of interleaved signals, a transmitter having a series of signal emitting means connectible with said segments for providing two groups or interleaved signals for transmission by said distributor, each group being of an opposite nature than the other group, a receiver distributor for receiving said flrstand second groups of interleaved signals, a recorder controlled by said receiver distributor for recording normal characters in response to signals being received as transmitted by said transmitter, and an error indicating means. forming. a part ofsaid recorder for recordinggan error indication in sp ns to f r any given element o'ila, signal code combination signals of. op osite nature not being receivcd by said receiver dis.

tr'ibutor.

,10. In a telegraph system, a, transmitter dis.- tributor including alternately arranged segments for transmitting a first and second group of interleaved signals, a transmitter having a series of signal emitting means connectible with said segments for providing two groups of interleaved signals for transmission by said distributor, each group being of an opposite nature than the other group, a receiver distributor including alternately arranged segments for receiving said first and second groups of interleaved signals, a recorder controlled by said receiver distributor for recording normal characters in response to signals being received as transmitted by said transmitter, and an error indicating means forming a part of said recorder for recording an error indication in response to for any given element of a signal code combination signals of opposite nature not being received by said receiver distributor.

11. In a telegraph system, a radio transmitting means, a transmitter distributor for operating said transmitting means to transmit a first and second group of interleaved signals, a transmitter associated with said distributor for providing for each message character two groups of interleaved signals for transmission by said distributor, each group being of an opposite nature than the other group, a radio receiver for receiving said interleaved signals, a receiver distributor controlled by said radio receiver, a recorder operable in response to the signals received by said receiver distributor for recording normal characters in response to signals being received as transmitted by said transmitter, and an error indicating means forming a part said recorder for recording an error indication in response to for any given element of a code combination signals of an opposite nature not being received by said receiver distributor.

12. In a telegraph system, a radio transmitting means, a transmitter distributor having alternately arranged segments for operating said transmitting means to transmit a first and second group of interleaved signals, a transmitter connected to said distributor for providing for each message character two groups of interleaved signals for transmission by said distributor, each group being of an opposite nature than the other group, a radio receiver for receiving said interleaved signals, a receiver distributor controlled by said radio receiver, a recorder operable in response to the signals received by said receiver distributor for recording normal characters in response to signals being received as transmitted l4" by'sa-id transmitter, and an" error indicating means forming a. part of said recorder for recjording an error indication in response to for any given element, of a code combination signals of opposite nature not being received by said receiver distributor.

; 13,, In a telegraph system, a transmitter distributorfor transmitting a first and second group of interleaved signals, a transmitter connected to said. distributor for providing two groups of interleaved; signals for. transmission by said dis: tributor, each group being of an opposite nature" than the other group, a receiver distributor including alternately arranged segments for receiving said first and second groups of inter-.

l'eayed signals, a recorder controlled by said receiver distributor for recording normal characters in response to signals being received as transmitted by said transmitter, and an error indicating means forming a part of said recorder for recording an error indication in response to for any given element. of a signal code combination signals of opposite nature not being received by said receiver distributor.

14. In a telegraph system including a transmitter distributor for transmitting a first and second group of interleaved signals, a transmitter connected to said distributor for providing two groups of interleaved signals for transmission by said distributor, said second group of signals bein inverted with respect to said first group of normal signals, a receiving distributor for receiving said groups of interleaved signals, a first recorder controlled by said receiving distributor and operable in accordance with the reception of said first group of signals, means controlled by said receiving distributor for reinverting said second group of received signals to return said signals to normal condition, and a 1 second recorder operable in accordance with said tributor for sending a first and second group of interleaved signals, a transmitter connected to said distributor for providing two groups of interleaved signals for transmission by said distributor, one group being of an opposite nature than the other group, a receiver distributor for receiving said first and second groups of interleaved signals, a first recorder controlled by said receiver distributor for recording normal characters in response to signals being received as transmitted, an error indicating means forming a part of said recorder and operable in response to for any given element of a signal code combination opposite signals not bein received, a second recorder connectible with said receiver distributor,

and switching means for connecting said second recorder to said receiver distributor to enable each of said recorders to record identical characters, said error indicating means being disabled upon the operation of said switching means.

16. In an error indicating telegraph system having transmitting and receiving stations, means at said transmitting station for sending each element of a signal code combination once in a normal manner and once in an inverted manner, receiving means at said receiving station for receiving said normal and inverted signals, a series of pairs of relays operable by said receiving means, one of the individual relays of each of said pairs of relays being responsive to normal signals and the other to inverted signals, recording means at said receiving station resnonsive to the opposite operation of the individual relays of each pair for recording normal characters, and an eror indicatin means forming a part of said recording means to record an error indicating character upon the failure of the individual relays of any pair to be oppositely operated with respect to each other.

17. In an error indicating telegraph system having transmitting and receiving stations, means at said transmitting station including a transmitter distributor for sending each element of a signal code combination once in a normal manner and once in an inverted manner, receiving means at said receiving station including a receiver distributor for receiving said normal and inverted signals, a series of pairs of relays operable by said receiving means, one of the individual relays of each of said pairs of relays being responsive to normal signals and the other to inverted signals, recording means at said receiving station responsive to the opposite operation of the individual relays of each pair for recording normal characters, and an error indicating means forming a part of said recording means to record an error indicating character upon the failure of the individual relays of any pair to be oppositely operated with respect to each other.

MARTHA W. C. POTTS, Executrix, Under the Last Will and Testament of Louis M. Potts, Deceased.

REFERENCES CITED Thefollowing references are of record in the file of this patent:

UNITED STATES PATENTS Bellescize Nov. 9, 1948 Disclaimer 2,512,038.L0m's M. Potts, deceased,"late of Evanston, 111., by Martha W. 0. Potts, eacecutm'w. ERROR DETECTING CODE SYSTEM. Patent dated June 20, 1950. Disclaimer filed Aug. 17, 1950, by bhe assignee, Teletype Goeporation. Hereby enters this disclaimer to claim 4 of said. patent.

[Ofiic'ial Gazette September 19, 1.950.] 

